Signs and symptoms are diagnostic indications of an illness, injury, or condition. While signs are objective and externally observable; symptoms are a person's reported subjective experiences.
A sign, for example, can be an elevated or lower than normal temperature or blood pressure; or an abnormal finding showing on medical imaging. A symptom is something out of the ordinary that is experienced by an individual such as feeling feverish, a headache or other pains in the body. Symptoms can be a result of the immune system's response to an infection, the physical manifestation of an abnormal body condition, or the effect of a consumed substance. Symptoms, though often indicative of a disease process, are not always diagnostically relevant, and can be idiopathic in nature.